Why aluminum cannot be soldered with tin solder. The process of soldering aluminum at home

Soldering aluminum at home is carried out by many self-taught craftsmen. Every man in the house can find a soldering iron, since this tool is indispensable. In production, and even at home, in order to solder aluminum, it is necessary to use special materials and devices. This type of soldering can be done using tin-lead solders 50 and 61. If you are going to do this type of work at home, this can be done in several ways and with different materials.

Remember that the main task is to remove the oxide film from the metal surface, and direct contact with air should not be allowed, for this, use rosin, mineral oil or alkali, and you can also use a saturated solution of copper sulfate.
In order to start considering the processes of soldering aluminum at home, you need to know some ways to prepare the material for this process.

Material preparation methods

For the first method, rosin is used to clean the soldering site. And after that, a soldering iron is immediately connected to the work, with which you press the skin to the place of soldering. Then you need to wipe the place of soldering with a sandpaper. Now it's time for the aluminum patch, which you can solder in the usual way.

Although rosin is often used in this processing method, mineral oil for a sewing machine is best.

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Second cleaning method. In the place where it is necessary to solder something, iron filings are additionally added to the rosin. With the help of such a mixture, a heated soldering iron rubs the place so that the solder will be as effective as possible. This effect is due to the fact that metal filings remove oxide from the surface, and this ensures maximum adhesion between the surfaces. This method does not require additional cleaning of the metal.

The third cleaning method is laborious and will take you a lot of time. But it is considered the most reliable. First you need to process the required area in order to remove the oxide film. Then, in the place where soldering will be carried out, it is necessary to create a plastic side, which will later serve as a bath.

You can make this bath from ordinary plasticine. At its bottom it is necessary to apply a layer of copper sulfate. Just remember that the bath is used where there is a large soldering area, and for minor damage you do not need it at all.

Now a bare copper wire is placed in this fixture. Its diameter is about 3 mm. Just remember that the wire should consist only of copper. The wire must be held at a distance of one millimeter from the work surface.

To do this, use some additional stand, and the wire that is in the bath must certainly make contact with the body. Then bring the contact from some current source, the voltage should be from 3 to 12 watts.

You can do all this with the help of two connecting ends, and a battery, a rectifier or the most common battery can pass for a power source. You need to supply all this with a light bulb that will be responsible for the nominal DC voltage.

It will light up when the aluminum surface comes into contact with the copper wire, which is lowered into the bath. If the light works, then the wire touched the bottom of the bath, and if not, then the whole process was interrupted.

After that, copper sulphate should come to a boil, and at this moment red copper is formed. You must rinse and dry the red layer. Proceed boldly to ordinary surface soldering.

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aluminum brazing process

Materials and tools:

• rosin;
• soldering iron;
• mineral oil;
• metal filings;
• copper sulfate;
• plasticine;
• welding pencil;
• lighter;
• piece of glass.

The welding stick resembles solder-sealant, thanks to it you can get a strong and reliable connection of parts, wires, aluminum tubes. Many refuse simple gas burners, and are increasingly inclined to a welding pencil.

But you need to take into account the fact that in the work of different devices there are pros and cons. The process of this type of tool is very simple, for this you need to set fire to the pencil.

For this kind of manipulation, a simple lighter is suitable, with which you set fire to the edge of the solder. The device will burn due to magnesium, which is part of it. It heats up to the temperature needed to melt the aluminum.

Under the action of high temperature, a molten mass is formed. You need to apply it to your work surface. The angle of impact of the pencil does not matter, since the resulting mass adheres very well to aluminum.

After the solder is removed from the working surface, the pencil stops working, but the aluminum mass continues to burn. After about 20 seconds, the entire surface will have the same temperature.

And after that, you can safely proceed to filling the aluminum into the work surface. Use a pencil or piece of glass for this purpose.

Hi all! Many people know that aluminum is soldered mainly in an argon environment with a special welding machine, but there is another option for working with a gas burner, and even a turbo lighter can be used on a small scale.

In general, this is not my first acquaintance with this wire, but the shopping experience is not very good, so I will share not only the test result, but also proven places to buy, so as not to get sample number 2, but let's start in order.

Characteristics

Diameter: 2.0mm
Length: 500 mm
Soft solder ISO 3677:~B-Zn98Al 381-400
Approximate composition (weight%): 2.4 Al - the rest is Zn
Melting point ºС: 360
Tensile strength (MPa): Up to 100 (Al)
Density (g/cm3): 7,0

Unpacking and appearance

The last and most profitable acquisition was sample no. 3 from banggood.

Came in a small gray package

The rod is additionally packed in a transparent zip-package.

5 meters cost me $8 with points, that is $1.6 per meter

White powder flux is visible in the center, the rod is moderately hard, looks like aluminum without oxidation

Comparison

The one on the far left was bought first. sample number 1 in Ali. It is absolutely identical in properties to sample number 3, but 3 meters cost me $12 , that is $4 behind meter which is almost three times more expensive. check current price

In the center sample number 2. It costs $5 3 meters or $1.7 behind meter, like sample no. 3

But as soon as you take the bag in your hand, you understand that this is a POS with a not very thick flux inside.

Two more samples $8 over 3 meters were never delivered, probably they were not even sent.

Testing

Aluminum eventually becomes covered with an oxide film, due to which the surface becomes matte, and so, before soldering surfaces must be cleaned to a shine, otherwise the solder will simply roll over the surface in balls, regardless of the degree of its heating. Sample #1

In general, it is correct to heat the part to a temperature of about 400 degrees, and then simply drive the rod, which will melt and fill the gaps, but I have little experience, so in order not to overheat the surface, I periodically bring the rod into the burner flame. If the temperature is low, the solder will roll over the surface in a ball, if it is sufficient, it will tin it.

The fracture test shows a good result - the break does not occur along the seam

Sample #2. It melts very well, emits a lot of smoke, stinks of burnt "aspirin". It sticks to aluminum, but if overheated, it burns out pretty quickly.

It is inconvenient to work because of the stench and the need to control the temperature.

Sample #3. I decided to solder the tubes with the outer walls

Trying to break the seam. After the tube popped out of the vise, I clamped it higher, taking it out of focus and noticed this only at the stage of creating gifs

But there is a photo of the result, which shows that the seam was not damaged.

And finally, let's splice an aluminum tube with a piece of "duralumin"

The tear test was also successful.

Results

An interesting wire - aluminum solders perfectly, filling even small gaps with itself, the main thing is that the joints are not dirty. It also sticks well to copper, but experienced people say that it is better to use other alloys to work with it, although this bar will also work for emergency field repairs.

The melting point of aluminum is about 660ºС, it would seem that you can use rods at 450-500 degrees, but you may encounter two problems:
1. A massive part up to 500 degrees needs to be warmed up with something else
2. You can overheat the soldering point and ruin the part

It seemed to me the best sample no. 3. Corresponds to the declared characteristics and is cheaper than the rest at least twice. There are also lots of different lengths to choose from:
1 meter - $2.89
2 meters - $4.39
3 meters - $6.39
5 meters - $9.89

Home craftsmen quite often have to deal with the problem of repair, as well as the manufacture of aluminum products. If there are no problems with machining (the metal is easily sawn, turned and bent), then the process of connecting the parts to each other causes difficulties.

We are not talking about welding, these are issues of large-scale repairs. Most often, you have to solder parts in the traditional way.

• The most common problem is leaky dishes, or broken parts of household aluminum utensils. Bonding is not always suitable, due to low heat resistance and poor aesthetics of the seam. Rivets cannot provide tightness. It remains to solder aluminum with tin.
• Another need for a quality connection is electrical appliances. Quite often it is necessary to connect aluminum conductors to terminals, or simply to the surface of electrical equipment. Splicing wires will also be more reliable if there is a strong solder instead of twisting.

Like any metal, aluminum can and should be soldered. It has good ductility and thermal conductivity. But there is a problem with adhesion. In the open air, the metal is instantly covered with a strong film of oxides, which, besides being a heat insulator, is almost impossible to apply solder to.

Therefore, a high-quality flux for soldering aluminum is the first assistant in the work. It can also be used to solder aluminum to other metals.

General principles for soldering aluminum at home

Little secrets. If you do not have a special flux at hand, you can use abrasive protection against instant surface oxidation:

• Vigorously rub the soldered area with a piece of brick. The resulting dust does not need to be blown off. Type a large amount of ordinary rosin on the tip of the soldering iron, and fill the place of soldering with it directly on top of the brick dust. Then irradiate the surface by strongly pressing the tip of the soldering iron onto the metal.

  With a flat cut, it is necessary, as it were, to rub dust into aluminum. The abrasive will remove the thin layer of oxide and bond with the solder. Fine sifted sand can be used.

• Another way is to use iron filings. You can simply grind off a thick nail with a medium-grained file. Pour liquid rosin into the place of soldering and fill it with sawdust. When the rosin hardens, we collect solder on the tip of the soldering iron and rub it intensively over the sawdust. The tin coating will provide instant protection against oxidation.

Use of transformer oil

Soldering aluminum at home is usually done with a soldering iron.

You can mix solder paste with transformer oil and apply it to a freshly cleaned surface. Then also intensively rub with a soldering iron until a stable layer of solder appears.

Important! Such work should be done with a hood, or in a well-ventilated area. Overheated oil emits acrid smoke.

And there is an easier way. We process the future place of soldering with fine sandpaper. Then immediately pour in the oil.

Once again, intensively rub the surface with sandpaper, after which we rub the solder with a heated soldering iron.

We pry off the tin layer with a thin screwdriver to check the strength of the connection. If the edges of the solder come off the aluminum, repeat the procedure again. After obtaining stable tinning, both copper and aluminum wire can be soldered to this place.

What solder is used for soldering aluminum

The choice of solder is influenced by the method of joining aluminum parts.

1. If you are using a regular soldering iron, you need a material with a low melting point. Electrical connections usually use traditional solder. These are the following types of alloys: zinc-tin, copper-tin and bismuth-tin. They are better known to us as amateur radio solders of the POS series.

   These alloys are easy to melt, they take away little heat from the soldering iron (which is important, given the high thermal conductivity of aluminum). In addition, such material is easy to buy at an affordable price. However, joints using low-melting solder have low strength. This method is suitable only for electrical installation.

   If you soldered the spout to an aluminum teapot, or patched up a burnt hole in a pan, the connection will quickly collapse under the influence of high temperatures.

   In extreme cases, you can use the common refractory solder TsOP-40, consisting of tin and zinc. Such a connection holds the temperature quite well, but has a low tensile strength.

2. For mechanically strong joints, refractory solders are used. In addition, they will not melt at high temperatures. The composition must necessarily include the actual aluminum.
   The most common alloys are aluminum-copper-silicon.

   Aluminum dissolves well in other components of the composition, and will provide a connection with the workpiece at the molecular level. Copper will add ductility, and silicon will make the connection strong. The favorite solder of home tinkers is the domestic composition 34A.

More expensive (this does not mean an increase in quality) - imported "Aluminum - 13". The advantages of such solders are that they can weld parts with high quality, which then work under load.

Of course, these solders do not reach the strength of arc welding, but repairing dishes with their help gives a good result.

However, aluminum-based solders melt at a temperature of about 600 ° C. With a soldering iron, this result cannot be achieved.

For mechanically strong and heat-resistant joints, aluminum soldering with a gas burner is used.

note

Despite the external similarity and the quality of the connection, soldering with a torch has nothing to do with welding. Only the solder is melted, the base metal of the workpiece remains solid during the entire process.

Advantages of soldering with a torch over welding in an argon environment:

How to solder with a torch

You can’t do without preparing the junction, as with soldering with a soldering iron. The metal should be cleaned of dirt, sanded until a smooth surface is obtained. Then you need to fix the parts with the help of any jig - be it clamps or a vice.

When working with a burner, aluminum blanks will heat up over the entire surface. And given the high thermal conductivity of the metal, there will simply be no place on the parts that you can grab with your hand, even with protective gloves.

The working area must be cleared of flammable objects and liquids. Provide intensive ventilation - even without caustic secretions, heated fluxes exude an unpleasant odor. Take care of fire extinguishers.

It is necessary to prepare wire solder with a margin in length. You won't be able to fully use each rod, leaving 10% of the length to hold the solder. And to stop heating and go for a new package is irrational.

Important! A better seam is obtained with continuous soldering. If you interrupted the process (forced), before continuing work, completely warm up the entire place of soldering, including already solidified solder. The same should be done when applying several layers. First we warm up the frozen layer, then we put the next one.

The burner flame is always directed away from you. There should be no objects in its path.

It is allowed to change the color of the aluminum billet to bright orange. The metal will not melt, and when heated to the maximum temperature, the solder will lay down more evenly.

Be sure to use flux. There are proven compounds based on lithium and potassium chlorides, as well as zinc chloride. These are such brands as F-59A, F-61A, F-64A. For higher temperature soldering, it is better to use F-34A. It contains sodium fluoride.

Flux for soldering aluminum can be prepared by hand. However, it is not recommended to do this, since caustic substances are necessarily included in its composition. It is better to buy a ready-made composition in the store.

Important! Inhaling flux fumes while soldering is very harmful. Use a respirator or portable exhaust.

There is a widespread belief that it is impossible to solder or tin aluminum (as well as alloys based on it) without special equipment for this.

Two factors are given as an argument:

1. upon contact with air, a chemically resistant and refractory oxide film (AL 2 O 3) is formed on the surface of the aluminum part, as a result of which an obstacle is created for the tinning process;
2. the soldering process is significantly complicated by the fact that aluminum melts at a temperature of 660°C (for alloys, this range is from 500 to 640°C). In addition, the metal loses its strength when, during the heating process, its temperature rises to 300 ° C (for alloys up to 250 ° C), which can cause a violation of the stability of aluminum structures.

Given the above factors, it is really impossible to solder aluminum with conventional means. The use of strong fluxes, combined with the use of special solders, will help to solve the problem. Let's consider these materials in detail.

Solder

Commonly used solder bases are tin (Sn), lead (Pb), cadmium (Cd), bismuth (Bi), and zinc (Zn). The problem is that aluminum practically does not dissolve in these metals (with the exception of zinc), which makes the connection unreliable.

By using a highly active flux and properly treating the joints, it is possible to use tin-lead solder, but it is better to refuse such a solution. Moreover, the solder joint based on the Sn-Pb system has low corrosion resistance. Applying a paint and varnish coating to the place of soldering allows you to get rid of this drawback.

For soldering aluminum parts, it is desirable to use solder based on silicon, copper, aluminum, silver or zinc. For example 34A, which consists of aluminum (66%), copper (28%) and silicon (6%), or the more common DSP-40 (Sn - 60%, Zn - 40%).

Note that the greater the percentage of zinc in the composition of the solder, the stronger the connection will be and the higher its resistance to corrosion.

High-temperature solder is considered to be solder consisting of metals such as copper, silicon and aluminum. For example, as the domestic solder 34A mentioned above, or its foreign analogue "Aluminium-13", which contains 87% aluminum and 13% silicon, which allows soldering at temperatures from 590 to 600 ° C.

Flux

When choosing a flux, it must be taken into account that not all of them can be active towards aluminum. We can recommend using for such purposes the products of a domestic manufacturer - F-59A, F-61A, F-64, they consist of ammonium fluoroborates with the addition of triethanolamine. As a rule, there is a mark on the vial - “for aluminum” or “for soldering aluminum”.

For high-temperature soldering, you should purchase flux, manufactured under the brand name 34A. It consists of potassium chloride (50%), lithium chloride (32%), sodium fluoride (10%) and zinc chloride (8%). Such a composition is most optimal if high-temperature soldering is performed.

Surface preparation

Before you start tinning, you must perform the following steps:

• degrease the surface with acetone, gasoline or any other solvent;
• remove the oxide film from the place where the soldering will be performed. For cleaning, sandpaper, an abrasive wheel or a brush with steel wire bristles are used. Alternatively, etching can be used, but this procedure is not so common due to its specificity.

It should be borne in mind that it will not be possible to completely remove the oxide film, since a new formation instantly appears in the cleaned place. Therefore, stripping is carried out not to completely remove the film, but to reduce its thickness in order to simplify the task of the flux.

Solder point heating

For soldering small parts, you can use a soldering iron with a power of at least 100W. Massive objects will require a more powerful heating tool.

The best option for heating is to use a gas burner or a blowtorch.

When using the burner as a heating tool, the following nuances should be taken into account:

• do not overheat the base metal, as it may melt. Therefore, the temperature must be regularly monitored during the process. This can be done by touching the heated element with solder. Melting the solder will let you know that the required temperature has been reached;
• oxygen should not be used to enrich the gas mixture, since it contributes to the strong oxidation of the metal surface.

Soldering instructions

The process of soldering aluminum parts does not have its own distinctive features, it is carried out in the same way as with steel or copper.

The algorithm of actions is as follows:

• the place of soldering is degreased and cleaned;
• parts are fixed in the desired position;
• the junction heats up;
• touch the solder rod (containing active flux) to the joint. If a flux-free solder is used, then a flux is applied to destroy the oxide film, after which a hard piece of solder is rubbed at the place of soldering.

A steel wire bristle brush is also used to break down the aluminum oxide film. With this simple tool, molten solder is rubbed onto an aluminum surface.

Soldering aluminum - full video instruction
https://www.youtube.com/watch?v=ESFInizLE9U

What to do if the necessary materials are not available?

When it is not possible to prepare all the materials needed for soldering, an alternative method can be used, which uses tin or tin-lead solder. As for the flux, it is replaced by rosin. In order not to form a new film of aluminum oxide in place of the old one, stripping is carried out under a layer of molten rosin.

The soldering iron, in addition to its direct purpose, will be used as a tool that destroys the oxide film. To do this, a special scraper is put on his sting. You can increase the effectiveness of the process by adding metal filings to the rosin.

The process is as follows:

• with a heated tin-plated soldering iron, rosin is melted at the place of soldering;
• when the rosin completely covers the surface, they begin to rub it with a soldering iron tip. As a result, metal filings and a sting destroy the aluminum oxide film. Since the layer of molten rosin does not allow air to penetrate to the aluminum surface, an oxide film does not form on it. As the film breaks down, tinning of the part will occur;
• when the tinning process is completed, the parts are joined and heated until the melting temperature of the solder is reached.

It must be warned that the process of soldering aluminum without special materials is a rather troublesome process with no guarantee of successful completion. Therefore, it is better not to waste your time and energy on such work, especially since the quality and reliability of such a connection will be doubtful.

It is much easier to buy active flux and high-temperature solder, with which soldering aluminum even at home will not cause difficulties.

Aluminum and its alloys are only slightly inferior in strength to steel, but they are very easy to process, have a decent appearance and have such excellent qualities as thermal and electrical conductivity. However, along with these properties, there is the difficulty of their soldering. The question of how to solder aluminum is asked not only by novice amateurs, but also by those who are not difficult to solder copper, brass and steel.

Soldering aluminum is a complex process, so you need to know all its technology.

It is not easy to work with aluminum because of its ability to instantly oxidize in air, as a result of which the surface is covered with a thin film of Al2O3 oxide, which has an increased resistance to aggressive environments. Therefore, special mercury fluxes or replaceable soldering tips are used, or, depending on the soldering method, the oxide is removed in various ways.

Before soldering aluminum, they resort to mechanical removal of the film, cleaning the workplace with a needle file, but the contact of aluminum with water or air leads to the initial state - the appearance of the same film.

For soldering aluminum, you can use a special flux.

Experts advise cleaning the place of soldering with a brick or sand, without removing the dust, but apply molten rosin directly on it, then rub it with a soldering iron, pressing hard with a sting. This will help break down the thin film that formed before the rosin was applied.

Also, stripped aluminum is poured with rosin and sprinkled with sawdust from an iron nail, obtained in the process of filing. Next, you need to tin the surface with a soldering iron, carefully rubbing it with a sting. Iron chips will destroy the film, while rosin will prevent the formation of a new film.

Chemical cleaning methods

It is important not to let the cleaned aluminum come into contact with air, for which the place of soldering is filled with flux or rosin, while heating it. Often small items, such as wires, are lowered directly into rosin or flux poured into a container.

In addition to the mechanical method of removing oxide, there are several so-called chemical methods.

Cleaning aluminum before soldering can be done with copper sulfate.

Purification with copper sulphate. The point where you need to make solder is cleaned with a needle file, moistened with two or three drops of copper sulfate solution. The aluminum base is connected to the negative pole of the battery or accumulator, a small piece of copper wire stripped and connected to the positive pole is lowered into the solution without touching the base. After turning on the 4.5 volt battery, a copper coating forms on aluminum after a short period of time. The desired part is then soldered to the dried copper.

Application of abrasive powder. A liquid paste is prepared by mixing the powder and transformer oil, which is applied to the cleaned surface and then rubbed with a soldering iron until a tin layer appears.

Another way is transformer. The product is connected to its minus, a copper wire containing several cores is connected to the plus. After the circuit is closed, micro-welding of aluminum with copper will occur. Soldering acid is used to speed up the process.

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Application of fluxes and solders

For soldering large parts, such as cooling radiators, soldering irons with high power (100-200 W) are used, soldering irons with a power of 60-100 W quite successfully cope with small elements. Of course, the place of solder does not have a special fortress, but this is not required.

At home, fluxes F-64, FTBf-A, FIM are suitable for soldering aluminum. Of course, you can use as a flux and aspirin, and technical vaseline, and grease, and soldering fat, and stearin.

Using special active fluxes, soldering is easier, they cope well with an oxide film, provided that the heating temperature is 250-360 ° C.

The solder is distributed over the entire surface of the connection, which leads to a strong connection of the parts. The flux must be removed using solvents, alcohol or a special liquid. The convenience of using such fluxes is that they are also used for soldering nickel, copper and steel.

As a rule, alloys used for brazing aluminum are 2 parts zinc and 8 parts tin, or 1 part copper and 99 parts tin, or 1 part bismuth and 30 parts tin. Ordinary solders POS. 40 and PIC. 60 also cope with the task.

Small holes (no more than 7 mm in diameter) in aluminum utensils can be soldered without a soldering iron. The existing enamel around the hole should be beaten off by 5 mm, lightly tapping with a hammer. Now you need to use a file or sandpaper to polish the metal to a shine, using a crumb of rosin or soldering acid, put a piece of tin into the pan on the hole and heat it over a spirit lamp, which provides spot heating without destroying the remaining enamel. The metal, melting, will completely close the hole.

So, having a desire, you can solder aluminum at home.